1. Field of the Invention
The invention relates to a semiconductor integrated circuit having an oscillator circuit.
2. Description of the Related Art
In general, a tuner, an imaging system or the like needs a reference clock signal with a small frequency drift. In order to generate such a reference clock signal, a mechanical oscillator (a quartz crystal oscillator, a ceramic oscillator) with a high Q value and a small frequency drift is used.
On the other hand, the tuner, the imaging system or the like is controlled by a control LSI. An operation clock signal for operating an internal circuit is needed inside the control LSI. Such an operation clock signal is generated by an oscillator circuit inside the LSI, but it is known that it generates electromagnetic radiation noise (power supply noise, signal radiation noise).
A switching regulator circuit in which electromagnetic radiation noise due to switching noise is reduced is described in Japanese Patent Application Publication No. 2003-153526.
However, interference is likely to occur between the operation clock signal generated by the oscillator circuit and the reference clock signal generated by the tuner, the imaging system or the like, and the interference noise is likely to cause a problem for an application device such as the tuner, the imaging system or the like.